A036260 Numbers k > 1 such that k mod ord2(k) is even, where ord2(k) is the order of 2 mod k.

2921, 3017, 3473, 3479, 5767, 5969, 6167, 6377, 6497, 6913, 7223, 7519, 7567, 7751, 9017, 9271, 10199, 10447, 11431, 11929, 12719, 13439, 13609, 14513, 16583, 17009, 17143, 18631, 18809, 19313, 20737, 21119, 22337, 22351, 22537

Offset

1,1

Comments

These are all composite since for prime p, ord2(p) | phi(p) = p-1, whence p mod ord2(p) = 1.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[3, 23000, 2], EvenQ[Mod[#, MultiplicativeOrder[2, #]]] &] (* Amiram Eldar, Jul 30 2020 *)

Crossrefs

Cf. A002326, A007733, A036259.

Sequence in context: A031552 A205253 A251353 * A180651 A180331 A043444

Adjacent sequences: A036257 A036258 A036259 * A036261 A036262 A036263

Keyword

nonn

Author

David W. Wilson

Extensions

Offset corrected by Amiram Eldar, Jul 30 2020

Status

approved